Fallback to Any type in case supertypes are empty

This can happen e.g. if all supertypes were on the cycle (A : B, B : A)
-- then SupertypesLoopChecker will cut all supertypes that are on cycle,
leaving set of supertypes empty.

Some clients in the compiler are not ready to work with empty list of
supertypes -- notably, CommonSupertypes.

^KT-23029 Fixed

core/descriptors/src/org/jetbrains/kotlin/types/AbstractClassTypeConstructor.java

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.types;
 
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
 import org.jetbrains.kotlin.descriptors.*;
 import org.jetbrains.kotlin.resolve.DescriptorUtils;
@@ -160,4 +161,14 @@ public abstract class AbstractClassTypeConstructor extends AbstractTypeConstruct
 
         return additionalNeighbours;
     }
+
+    @Nullable
+    @Override
+    protected KotlinType defaultSupertypeIfEmpty() {
+        if (KotlinBuiltIns.isSpecialClassWithNoSupertypes(this.getDeclarationDescriptor())) {
+            return null;
+        } else {
+            return getBuiltIns().getAnyType();
+        }
+    }
 }